Marking, for example the name and logo of a manufacturer, a brand name or performance data of a product are generally indicated on products. Those that have glass or ceramic surfaces bear the markings on these surfaces. Such products are for example bulbs of light sources. Moreover labels, decorations and markings are also applied to the surface of household glass and ceramic goods as well as laboratory appliances.
The markings, labels and decorations can be manufactured by using ink materials that are stamped on the glass and ceramic surfaces, and then are burnt in so that the marking can be durable.
Several compositions for ink materials are known that are suitable for stamping and burning in, among others, on lamp bulbs. However, the known materials have lead content, which is undesirable.
From 1st of Jul. 2006, preparations containing lead cannot be used for marking glass parts of light sources in the European market any more, as it is stated in the 2002/95/EC Directive of the European Parliament and the Council of Europe. This Directive restricts the lead content in different compositions, semi-finished and finished products drastically. Considering that the restriction is obligatory both for manufacturers and for distributors, products containing lead will not be manufactured or sold after the date mentioned above.
U.S. Pat. No. 1,538,890 discloses an ink composition for glass. This ink comprises an intimate mixture of about 70% by weight of silver oxide and about 30% by weight of lead borate, mixed in the proportion of about 65% by weight to about 35% by weight of glycerin. Due to the lead borate content of the ink composition, it does not meet the requirements of lead-free composition and thus is harmful to the environment.
U.S. Pat. No. 2,254,865 relates to ink and, more particularly, to ink, which may be applied to the surface of glass or other smooth material, to produce thereon a monogram, trademark or other indicia. The patented ink composition comprises about 73.7% by weight of glycerin. This considerable amount of vehicle material is disadvantageous.
Thus there is a particular need for an ink composition, which meets the requirements of the above referenced Directive and still has good stamping, burning in and lifetime properties.